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STABILISATION OF A LANDSLIP

Cracking and settlement of road surface, March 2001

Beach Road provides vital vehicular access to the beach and properties at Babbacombe, Torquay. The narrow road traverses the steep coastal slope which is underlain by strata of Devonian age. Strong Limestone crops out in the upper levels, thrust-faulted over weak shale. Ancient shallow landslides in the weak, sheared shale have caused progressive cracking and settlement of Beach Road.

In 2001 Frederick Sherrell Ltd were commissioned by Torbay Council Environment Directorate to investigate the landslide and advise on remedial works. Geotechnical Engineering Ltd drilled 5 exploratory boreholes using compact, lightweight Pioneer Rigs, to minimise surcharge loads on the landslide.

The boreholes were equipped with inclinometers and piezometers to monitor movement of the ground and groundwater levels in the slip zone. The study demonstrated that the landslip affected up to 4m thickness of unstable shaly clays beneath the road.

Results of inclinometer monitoring


Stability Analysis

A reticulated mini-pile retaining structure was devised to stabilise the ground beneath the damaged road, and the works were constructed by South West Highways Ltd during the winter season of 2002/2003.

Drilling of mini-pile using compact, lightweight,
air-flush percussion rig



Stabilisation works showing reticulated piles and
completed reinforced concrete ground beam